Refreshing The Form Using PHP

I have a web form that utilizes PHP to update a serial number file on the server. I would like to show the user what the next number will be by refreshing the page after the user submits the original page. For example, if the current serial number is 10 and the user submits the page to print a series of serialized labels (say 3), then the next starting serial number will be 13. I would like to refresh the page showing 13 in the serial number page field. How do I do this?
Any help would be appreciated. Thanks...

You did not specify that you are using a database. If so presumably MySQL.
You will need to use MYISAM as it provides serial sequences unlike INNODB.
If not using DB you can use the $_POST['fieldname'] where fieldname is a
hidden field that is incremented with each iteration.

Thank you all for trying to help. I have tried several things to include adding a javascript function to my form to repopulate the updated field. That seems to work okay for now until I get a better solution. I wish I could add a better description of the system but it is an intricate set of forms using a combo of HTML, Javascript, CSS, XML, PHP and Oracle SQL. Thanks again...